Cleaning method for photo masks and apparatus therefor

ABSTRACT

In a method of cleaning a photo mask, the photo mask is placed on a support such that a patterned surface faces down, and an adhesive sheet is applied to edges of a backside surface of the photo mask.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 63/031,071 filed on May 28, 2020, the entire contents of which areincorporated herein by reference.

BACKGROUND

A lithographic apparatus projects a pattern from a patterning device(e.g., a photo mask) onto a layer of radiation-sensitive material(resist) provided on the semiconductor substrate. When a photo mask isnot used (stored) or transferred from a storage to an lithographyapparatus, such as a stepper or a scanner, the photo mask isappropriately protected from contamination such as dust or particles bybeing placed in a mask case (pod).

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic view of an extreme ultraviolet (EUV) lithographysystem with a laser produced plasma (LPP) EUV radiation source,constructed in accordance with some embodiments of the presentdisclosure.

FIG. 2 is a schematic view of an EUV lithography system exposure toolaccording to embodiments of the disclosure.

FIG. 3 is a schematic cross-sectional view of a mask pod device.

FIG. 4 shows a configuration of restraining supporters of the mask poddevice.

FIG. 5 shows a configuration when a photo mask is in contact with therestraining supporters.

FIG. 6 shows a configuration of a cleaning device and cleaning operationaccording to an embodiment of the disclosure.

FIG. 7 shows a configuration of a cleaning device and cleaning operationaccording to an embodiment of the disclosure.

FIG. 8 shows a configuration of a cleaning device and cleaning operationaccording to an embodiment of the disclosure.

FIG. 9 shows a configuration of a cleaning device according to anembodiment of the disclosure.

FIG. 10 shows a configuration of a cleaning device and cleaningoperation according to an embodiment of the disclosure.

FIG. 11 shows a configuration of a cleaning device and cleaningoperation according to an embodiment of the disclosure.

FIG. 12 shows a manual operation of a cleaning operation according to anembodiment of the disclosure.

FIGS. 13A and 13B show process flows of cleaning an EUV photo maskaccording to embodiments of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof the invention. Specific embodiments or examples of components andarrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, dimensions of elements are not limited to thedisclosed range or values, but may depend upon process conditions and/ordesired properties of the device. Moreover, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed interposing the first and second features, suchthat the first and second features may not be in direct contact. Variousfeatures may be arbitrarily drawn in different scales for simplicity andclarity. In the accompanying drawings, some layers/features may beomitted for simplification.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The device may be otherwise oriented (rotated 90 degrees orat other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. In addition, the term“made of” may mean either “comprising” or “consisting of.” Further, inthe following fabrication process, there may be one or more additionaloperations in between the described operations, and the order ofoperations may be changed. In the present disclosure, the phrase “atleast one of A, B and C” means either one of A, B, C, A+B, A+C, B+C orA+B+C, and does not mean one from A, one from B and one from C, unlessotherwise explained. Materials, configuration, dimensions and/oroperations explained with one embodiment can be applied to otherembodiments, and detailed explanation thereof may be omitted.

The present disclosure is generally related to extreme ultraviolet (EUV)lithography system and methods. Embodiments disclosed herein aredirected to an improved method and apparatus for cleaning an extremeultraviolet (EUV) photo mask.

The need for protection from particulate matter (i.e., dust, dirt, etc.)contaminating objects of interest is required in many fields ofapplication, including applications in semiconductor manufacturing suchas extreme ultraviolet lithography. A lithographic apparatus projects apattern from a patterning device (e.g., a photo mask, or a reticle) ontoa layer of radiation-sensitive material (resist) provided on thesemiconductor substrate. The wavelength of radiation used by alithographic apparatus to project a pattern onto a substrate determinesthe minimum size of features that can be formed on that substrate. Alithographic apparatus that uses extreme ultraviolet radiation, beingelectromagnetic radiation having a wavelength within the range 4-20 nm,may be used to form smaller features on a substrate than a relatedlithographic apparatus (which may for example use electromagneticradiation with a wavelength of 193 nm).

The patterning device (photo mask or reticle) is protected from particlecontamination by a pellicle. The pellicle is located away from thepatterning device and is out of the focal plane of a lithographicapparatus in use. Because the pellicle is out of the focal plane of thelithographic apparatus, contamination particles which land on thepellicle are out of focus in the lithographic apparatus. Consequently,images of the contamination particles are not projected onto thesubstrate. If the pellicle were not present, then a contaminationparticle which landed on the patterning device would be projected ontothe substrate and would introduce a defect into the projected pattern.

The photo mask with or without a pellicle is stored in a mask pod deviceand the mask pod device is stored in a photo mask library (stocker orstorage) when not used, and transferred from the photo mask library toan EUV lithography apparatus (e.g., an EUV scanner). In the presentdisclosure, the terms mask, photomask, and reticle are usedinterchangeably. In addition, the term resist and photoresist are usedinterchangeably. In some embodiments, the mask is a reflective mask.

FIG. 1 shows a schematic view of an EUV lithography system with a laserproduced plasma (LPP) EUV radiation source in accordance with someembodiments of the present disclosure. The EUV lithography systemincludes an EUV radiation source 100 (an EUV light source) to generateEUV radiation, an exposure device 200, such as a scanner, and anexcitation laser source 300. As shown in FIG. 1, in some embodiments,the EUV radiation source 100 and the exposure device 200 are installedon a main floor MF of a clean room, while the excitation laser source300 is installed in a base floor BF located under the main floor. Eachof the EUV radiation source 100 and the exposure device 200 are placedover pedestal plates PP1 and PP2 via dampers DMP1 and DMP2,respectively. The EUV radiation source 100 and the exposure device 200are coupled to each other by a coupling mechanism, which may include afocusing unit. In some embodiments, a lithography system includes theEUV radiation source 100 and the exposure device 200. In one particularexample, the EUV radiation source 100 generates an EUV light with awavelength centered at about 13.5 nm. In the present embodiment, the EUVradiation source 100 utilizes a mechanism of laser-produced plasma (LPP)to generate the EUV radiation.

The exposure device 200 includes various reflective optical components,such as convex/concave/flat mirrors, a mask holding mechanism includinga mask stage, and wafer holding mechanism, e.g., a substrate holdingmechanism. The EUV radiation generated by the EUV radiation source 100is guided by the reflective optical components onto a mask secured onthe mask stage. In some embodiments, the mask stage includes anelectrostatic chuck (e-chuck) to secure the mask. Because gas moleculesabsorb EUV light, the lithography system for the EUV lithographypatterning is maintained in a vacuum or a-low pressure environment toavoid EUV intensity loss. The exposure device 200 is described in moredetail with respect to FIG. 2. In some embodiments, a reticle istransferred into the exposure device 200. As noted, the exposure device200 is maintained under a vacuum environment and the reticle is mountedover a substrate, with a photo resist layer disposed on the substrate.The reticle has a pellicle mounted over the reticle. After transferringthe reticle with the pellicle into the exposure device 200, the airpressure in the enclosure between the reticle and the pellicle isequalized with the vacuum environment of the exposure device 200 throughthe holes in the mounting fixture (the frame). The EUV radiationgenerated by the EUV radiation source 100 is directed by the opticalcomponents to project the mask on the photo resist layer of thesubstrate. In some embodiments, after the exposure of the mask on thephoto resist layer of the substrate, the reticle with the pellicle istransferred out of the exposure device 200. After transferring thereticle with the pellicle out of the exposure device 200, the airpressure in the enclosure between the reticle and the pellicle isequalized with the atmospheric pressure outside the exposure device 200through the holes in the mounting fixture.

The exposure device 200 includes a projection optics module for imagingthe pattern of the mask on to a semiconductor substrate with a resistcoated thereon secured on a substrate stage of the exposure device 200.The projection optics module generally includes reflective optics. TheEUV radiation (EUV light) directed from the mask, carrying the image ofthe pattern defined on the mask, is collected by the projection opticsmodule, thereby forming an image on the resist.

As shown in FIG. 1, the EUV radiation source 100 includes a dropletgenerator 115 and a LPP collector mirror 110, enclosed by a chamber 105.The droplet generator 115 generates a plurality of target droplets DP,which are supplied into the chamber 105 through a nozzle 117. In someembodiments, the target droplets DP are tin (Sn), lithium (Li), or analloy of Sn and Li. In some embodiments, the target droplets DP eachhave a diameter in a range from about 10 microns (μm) to about 100 μm.For example, in an embodiment, the target droplets DP are tin droplets,each having a diameter of about 10 μm, about 25 μm, about 50 μm, or anydiameter between these values. In some embodiments, the target dropletsDP are supplied through the nozzle 117 at a rate in a range from about50 droplets per second (i.e., an ejection-frequency of about 50 Hz) toabout 50,000 droplets per second (i.e., an ejection-frequency of about50 kHz). For example, in an embodiment, target droplets DP are suppliedat an ejection-frequency of about 50 Hz, about 100 Hz, about 500 Hz,about 1 kHz, about 10 kHz, about 25 kHz, about 50 kHz, or anyejection-frequency between these frequencies. The target droplets DP areejected through the nozzle 117 and into a zone of excitation ZE (e.g., atarget droplet location) at a speed in a range from about 10 meters persecond (m/s) to about 100 m/s in various embodiments. For example, in anembodiment, the target droplets DP have a speed of about 10 m/s, about25 m/s, about 50 m/s, about 75 m/s, about 100 m/s, or at any speedbetween these speeds.

The excitation laser beam LR2 generated by the excitation laser source300 is a pulsed beam. The laser pulses of laser beam LR2 are generatedby the excitation laser source 300. The excitation laser source 300 mayinclude a laser generator 310, laser guide optics 320 and a focusingapparatus 330. In some embodiments, the laser generator 310 includes acarbon dioxide (CO₂) or a neodymium-doped yttrium aluminum garnet(Nd:YAG) laser source with a wavelength in the infrared region of theelectromagnetic spectrum. For example, the laser source 310 has awavelength of 9.4 μm or 10.6 μm in an embodiment. The laser light beamLR0 generated by the excitation laser source 300 is guided by the laserguide optics 320 and focused, by the focusing apparatus 330, into theexcitation laser beam LR2 that is introduced into the EUV radiationsource 100. In some embodiments, in addition to CO₂ and Nd:YAG lasers,the laser beam LR2 is generated by a gas laser including an excimer gasdischarge laser, helium-neon laser, nitrogen laser, transversely excitedatmospheric (TEA) laser, argon ion laser, copper vapor laser, KrF laseror ArF laser; or a solid state laser including Nd:glass laser,ytterbium-doped glasses or ceramics laser, or ruby laser. In someembodiments, a non-ionizing laser beam LR1 is also generated by theexcitation laser source 300 and the laser beam LR1 is also focused bythe focusing apparatus 330.

In some embodiments, the excitation laser beam LR2 includes a pre-heatlaser pulse and a main laser pulse. In such embodiments, the pre-heatlaser pulse (interchangeably referred to herein as the “pre-pulse) isused to heat (or pre-heat) a given target droplet to create alow-density target plume with multiple smaller droplets, which issubsequently heated (or reheated) by a pulse from the main laser (mainpulse), generating increased emission of EUV light compared to when thepre-heat laser pulse is not used.

In various embodiments, the pre-heat laser pulses have a spot size about100 μm or less, and the main laser pulses have a spot size in a range ofabout 150 μm to about 300 μm. In some embodiments, the pre-heat laserand the main laser pulses have a pulse-duration in the range from about10 ns to about 50 ns, and a pulse-frequency in the range from about 1kHz to about 100 kHz. In various embodiments, the pre-heat laser and themain laser have an average power in the range from about 1 kilowatt (kW)to about 50 kW. The pulse-frequency of the excitation laser beam LR2 ismatched with the ejection-frequency of the target droplets DP in anembodiment.

The laser beam LR2 is directed through windows (or lenses) into the zoneof excitation ZE. The windows adopt a suitable material substantiallytransparent to the laser beams. The generation of the laser pulses issynchronized with the ejection of the target droplets DP through thenozzle 117. As the target droplets move through the excitation zone, thepre-pulses heat the target droplets and transform them into low-densitytarget plumes. A delay between the pre-pulse and the main pulse iscontrolled to allow the target plume to form and to expand to an optimalsize and geometry. In various embodiments, the pre-pulse and the mainpulse have the same pulse-duration and peak power. When the main pulseheats the target plume, a high-temperature plasma is generated. Theplasma emits EUV radiation, which is collected by the collector mirror110. The collector mirror 110, an EUV collector mirror, further reflectsand focuses the EUV radiation for the lithography exposing processesperformed through the exposure device 200. A droplet DP that does notinteract with the laser pulses is captured by the droplet catcher 85.

FIG. 2 shows a schematic view of an EUV lithography (EUVL) exposure toolin accordance with some embodiments of the present disclosure. The EUVLexposure tool of FIG. 2 includes the exposure device 200 that shows theexposure of photoresist coated substrate, a target semiconductorsubstrate 210, with a patterned beam of EUV light. The exposure device200 is an integrated circuit lithography tool such as a stepper,scanner, step and scan system, direct write system, device using acontact and/or proximity mask, etc., provided with one or more optics205 a, 205 b, for example, to illuminate a patterning optic, such as areticle, e.g., a reflective mask 205 c, with a beam of EUV light, toproduce a patterned beam, and one or more reduction projection optics205 d, 205 e, for projecting the patterned beam onto the targetsemiconductor substrate 210. A mechanical assembly (not shown) may beprovided for generating a controlled relative movement between thetarget semiconductor substrate 210 and patterning optic, e.g., areflective mask 205 c. As further shown, the EUVL exposure tool of FIG.2, further includes the EUV radiation source 100 including a plasmaplume 23 at the zone of excitation ZE emitting EUV light in the chamber105 that is collected and reflected by a collector mirror 110 into theexposure device 200 to irradiate the target semiconductor substrate 210.In some embodiments, the mask pod device 10 is designed and manufacturedaccording to the Standard Mechanical Interface (SMIF) standards, such asRSP200 pod.

FIG. 3 shows a configuration of a mask pod device 10 in which an EUVphoto mask 12 is stored. The EUV photo mask 12 includes a substrate12-1, a multilayer Mo/Si stack 12-2 of multiple alternating layers ofsilicon and molybdenum, a capping layer 12-3, an absorber layer 12-4 anda backside conductive layer 12-5 formed on the backside of the substrate12-1.

The substrate 12-1 is formed of a low thermal expansion material in someembodiments. In some embodiments, the substrate is a low thermalexpansion glass or quartz, such as fused silica or fused quartz. In someembodiments, the low thermal expansion glass substrate transmits lightat visible wavelengths, a portion of the infrared wavelengths near thevisible spectrum (near infrared), and a portion of the ultravioletwavelengths. In some embodiments, the low thermal expansion glasssubstrate absorbs extreme ultraviolet wavelengths and deep ultravioletwavelengths near the extreme ultraviolet. In some embodiments, the sizeof the substrate 10 is 152 mm×152 mm (or 150 mm×150 mm) having athickness of about 20 mm. The shape of the substrate 12-1 is square orrectangular.

In some embodiments, the Mo/Si multilayer stack 12-1 includes from about30 alternating layers each of silicon and molybdenum to about 60alternating layers each of silicon and molybdenum. In certainembodiments, from about 40 to about 50 alternating layers each ofsilicon and molybdenum are formed. In some embodiments, the reflectivityis higher than about 70% for wavelengths of interest e.g., 13.5 nm. Eachlayer of silicon and molybdenum is about 2 nm to about 10 nm thick. Insome embodiments, the layers of silicon and molybdenum are about thesame thickness. In other embodiments, the layers of silicon andmolybdenum are different thicknesses. In some embodiments, the thicknessof each silicon layer is about 4 nm and the thickness of each molybdenumlayer is about 3 nm.

The capping layer 12-3 is disposed over the Mo/Si multilayer 12-2 toprevent oxidation of the multilayer stack 12-2 in some embodiments. Insome embodiments, the capping layer 12-3 is made of ruthenium, aruthenium alloy (e.g., RuNb, RuZr, RuZrN, RuRh, RuNbN, RuRhN, RuV orRuVN) or a ruthenium based oxide (e.g., RuO₂, RuNbO, RiVO or RuON),having a thickness of from about 2 nm to about 10 nm.

The absorber layer 12-4 is disposed over the capping layer 12-3 andcircuit patterns are formed therein. In some embodiments, the absorberlayer 25 is Ta-based material. In some embodiments, the absorber layer12-4 is made of TaN, TaO, TaB, TaBO or TaBN having a thickness fromabout 25 nm to about 100 nm. In certain embodiments, the absorber layer12-4 thickness ranges from about 50 nm to about 75 nm. In otherembodiments, the absorber layer 12-4 includes a Cr based material, suchas CrN, Cr0 and/or CrON. In some embodiments, the absorber layer 12-4has a multilayered structure of Cr, CrO or CrON. In some embodiments, anantireflective layer (not shown) is optionally disposed over theabsorber layer 12-4. The antireflective layer is made of a silicon oxidein some embodiments, and has a thickness of from about 2 nm to about 10nm. In other embodiments, a TaBO layer having a thickness in a rangefrom about 12 nm to about 18 nm is used as the antireflective layer. Insome embodiments, the thickness of the antireflective layer is fromabout 3 nm to about 6 nm.

In some embodiments, the backside conductive layer 12-5 is made of TaB(tantalum boride) or other Ta based conductive material. In otherembodiments, the backside conductive layer 45 is made of a Cr basedconductive material (CrN or CrON). A thickness of the backsideconductive layer 45 is in a range from about 50 nm to about 400 nm insome embodiments. In other embodiments, the backside conductive layer 45has a thickness of about 50 nm to about 100 nm. In certain embodiments,the thickness is in a range from about 65 nm to about 75 nm.

The mask pod device 10 includes an outer pod 15 and an inner pod 16enclosed by the outer pod 15. The outer pod 15 includes an upper case15-1 and a bottom case 15-2, and the inner pod includes a upper cover16-1 and a bottom cover 16-2. As shown in FIG. 3, the EUV photo mask 12is placed in the inner pod face down (the absorber layer faces down tothe bottom cover 16-2). For the sake of clarity of illustration, thepellicle is not shown installed over the patterned surface (absorberlayer). However, it should be noted that a pellicle is installed overthe photo mask 12.

The bottom cover 16-2 of the inner pod 16 includes one or more supports16-3 to support the front surface of the photo mask 12, and the uppercover 16-1 of the inner pod 16 includes one or more restrainingsupporters 16-4 to support the backside of the photo mask 12. In someembodiments, as shown in FIG. 4, which is a view from the back surfaceof the photo mask, four restraining supporters 16-4 support the fourcorners of the photo mask 12.

FIG. 5 shows a cross sectional view when the upper cover 16-2 is closedand the restraining supporters 16-4 are in contact with the photo mask12. It is noted that FIG. 5 is upside-down unlike FIG. 3.

An EUV photo mask 12 and the mask pod device have a specific shape anddimension. For example, the four corners are rounded with a radius ofabout 2 mm to about 3 mm, and the edge between the main surface and theside surface is chamfered by an amount of about 0.2 mm to about 0.6 mm,as shown in FIG. 5. The chamfered angle is about 45 degrees as shown inFIG. 5. In contrast, the restraining supporters 16-4 have an inclinedsurface on which the chamfered edge of the photo mask contacts, but hasan angle of 34.4 degrees, as shown in FIG. 5. Because of the differencein the angles, the chamfered corner of the photo mask may damage or diginto the restraining supporter 16-4, creating a particle 18. Such aparticle may affect the flatness of the photo mask 12 when mounted on amask stage in an EUV lithography apparatus. To clean a photo mask, anair blower or a cleaning wiper has been used, but they may remove theparticle only from the flat surface of the photo mask. Accordingly, itis necessary to effectively remove the particles from the edge or thebackside of the photo mask 12.

According to embodiments of the present disclosure, a cleaning device20A as shown in FIG. 6 is used to remove the particle on the edge or thebackside of the photo mask 12. In some embodiments, the cleaning device20A includes an adhesive or sticky sheet or tape 22 attached to a body24A or 24B as shown in FIG. 6. In some embodiments, the adhesive sheet22 includes an elastomer or a gelatinous material. In some embodiments,the adhesive sheet 22 is made of silicone, astyrene-ethylene-butylene-styrene copolymer, astyrene-ethylene-propylene-styrene copolymer, or any other suitableadhesive material.

In some embodiments, the adhesive sheet 22 is disposed on at least onemain surface of the body 24A or 24B. In some embodiments, the body 24Ahas a cuboid shape, and the adhesive sheet 22 is attached to a main flatsurface of the body 24A. In other embodiments, the body 24B has at leastone curved surface (convex or concave), on which the adhesive sheet 22is attached. Further, in some embodiments, a handling grip 28 (see, FIG.9) is attached to the body 24 through a rod 26. As shown in FIG. 6, theadhesive sheet 22 of the cleaning device 20A is applied to the chamferededge of the backside of the photo mask 12 from the backside of the photomask 12.

In some embodiments, the photo mask 12 is placed on the supports 16-3 ofthe bottom cover 16-2 by opening or removing the upper cover 16-1, andin other embodiments, the photo mask 12 is placed on another supporttable or stage. The particles on the edge of the photo mask 12 isremoved by sliding the cleaning device 20 along and/or across the edgesof the photo mask 12, as shown in FIG. 6. In some embodiments, the mainsurface of the adhesive sheet 22 is inclined with respect to the backsurface of the photo mask 12 by an angle θ in a range from about 0degrees to about 90 degrees. In other embodiments, the angle θ is in arange from about 30 degrees to about 75 degrees, and in certainembodiments, the angle θ is in a range from about 40 degrees to about 50degrees. The cleaning device 20A is operated manually in someembodiments, and is operated mechanically in other embodiments. Byadjusting the angle, the chamfered edge at the front face and the sideface can be cleaned. In some embodiments, the chamfered edge at the backface is not treated by the cleaning device 20A.

In some embodiments, the thickness of the adhesive sheet 22 is in arange from about 1 mm to about 5 mm. In some embodiments, the adhesivesheet 22 is replaceable with a new adhesive sheet.

In some embodiments, the body 24A, 24B is made of an elastic material,such as rubber or sponge. The elastic material of the body 24A, 24B canapply appropriate pressure to the adhesive sheet 22 when applied to thephoto mask 12, which improves particle removal efficiency. When theadhesive sheet 21 has a sufficient elasticity, the body 24A, 24B can bemade of a non-elastic material, such as glass, plastic, ceramic ormetal.

FIG. 7 shows a configuration of a cleaning device and cleaning operationaccording to an embodiment of the present disclosure. Materials,configuration, dimensions and/or operations explained with aboveembodiments can be applied to the following embodiments, and detailedexplanation thereof may be omitted.

In some embodiments, a cleaning device 20B, as shown in FIG. 7, includesan adhesive or sticky sheet or tape 22 attached to a body 24C. In someembodiments, the adhesive sheet 22 includes an elastomer or a gelatinousmaterial. In some embodiments, the adhesive sheet 22 is made ofsilicone, a styrene-ethylene-butylene-styrene copolymer, astyrene-ethylene-propylene-styrene copolymer, or any other suitableadhesive material. In some embodiments, the body 24C has a cylindricalshape around which the adhesive sheet 22 is wrapped. Further, in someembodiments, a handling grip 28 (see, FIG. 9) is attached to the body 24through a rod 26.

As shown in FIG. 7, the adhesive sheet 22 of the cleaning device 20B isapplied to the chamfered edge of the backside of the photo mask 12 fromthe backside of the photo mask 12. In some embodiments, the body 24C islinearly moved along the axis of the rod 26 manually or mechanically.

FIG. 8 shows a configuration of a cleaning device and cleaning operationaccording to an embodiment of the present disclosure. Materials,configuration, dimensions and/or operations explained with aboveembodiments can be applied to the following embodiments, and detailedexplanation thereof may be omitted.

In some embodiments, as shown in FIG. 8, the cleaning device 20C isrotational type, in which the body 24C with the adhesive sheet 22rotates around the axis of the rod 26. In some embodiments, as shown inFIG. 9, the rod is rotated by a driving mechanism 27, such as a motor,disposed in the grip 28. In some embodiments, the driving mechanism 27also moves the rod 26 linearly in a reciprocating manner as shown inFIG. 7. In some embodiments, the speed and directions of the movement ofthe rod 26 are adjustable. In some embodiments, the rod 26 is flexibleand can be bent to fit the chamfered edges of the photo mask 12. In someembodiments, the driving mechanism 27 also applies vibrations to thebody through the rod 26. The vibration is in an ultrasound range in someembodiments, and in other embodiments, the vibration is about 1 Hz to 10kHz.

FIG. 10 shows a configuration of a cleaning device and cleaningoperation according to an embodiment of the present disclosure.Materials, configuration, dimensions and/or operations explained withabove embodiments can be applied to the following embodiments, anddetailed explanation thereof may be omitted.

FIG. 10 shows a cleaning device according to another embodiment of thepresent disclosure. In some embodiments, in the cleaning device 20Dshown in FIG. 10, an adhesive sheet or tape 22A is wound around a firstrod or body 26-1 and one end of the adhesive sheet or tape 22A isattached to a second rod or body 26-2, such that by rotating the secondrod or body 26-2, the adhesive sheet or tape 22A is released from thefirst rod or body 26-1 and wound around the second rod or body 26-2. Theadhesive sheet or tape 22A is applied to the edge of the photo mask 12to remove particles. The used part of the adhesive sheet or tape 22A istransferred to the second rod or body 26-2 and thus a new and freshportion of the adhesive sheet or tape 22A can be applied to the nextcleaning part of the photo mask 12.

In some embodiments, the rotation of the second rod or body 26-2 or themovement of the adhesive sheet or tape 22A is continuous. In otherembodiments, the rotation of the second rod or body 26-2 or the movementof the adhesive sheet or tape 22A is a step-wise-manner. For example,after the one edge of the four sides of the photo mask 12 is cleaned,the adhesive sheet or tape 22A is refreshed by the rotational movementof the second rod or body 26-2. In other embodiments, the adhesive sheetor tape 22A is refreshed after a time interval.

In some embodiments, similar to FIG. 9, at least the second rod or body26-2 is coupled to a driving mechanism 27, such as a motor, to controlthe rotational operation of the second rod or body 26-2. In otherembodiments, the first rod or body 26-1 is also coupled to another motoror the same motor through one or more gears. In some embodiments, therotational speed is adjustable. In some embodiments, the drivingmechanism 27 also applies vibrations to the body through the rod 26. Thevibration is in an ultrasound range in some embodiments, and in otherembodiments, the vibration is about 1 Hz to 10 kHz.

In some embodiments, the main surface of the adhesive sheet or tape 22Ais inclined with respect to the back surface of the photo mask 12 by anangle θ′ in a range from about 0 degrees to about 90 degrees. In otherembodiments, the angle θ′ is in a range from about 30 degrees to about75 degrees, and in certain embodiments, the angle θ′ is in a range fromabout 40 degrees to about 50 degrees. By adjusting the angle, thechamfered edge at the front face and the side face can be cleaned. Insome embodiments, the chamfered edge at the back face is not treated bythe cleaning device 20D.

In some embodiments, the angle θ′ shown in FIG. 10 and the angle θ shownin FIGS. 6-8 can be adjusted or changed by a mounting jig 30 as shown inFIG. 11. In some embodiments, the mounting jig 30 includes a base platehaving arc portion, which can be an outer periphery of the base plate oran arch shaped slit formed in the base plate, and a movable plate 32that moves along the arc portion. The movable portion 32 is coupled tothe cleaning device 20 or 20A, and by moving the movable plate 32 alongthe arc portion, the angle θ′ or θ, can be changed.

In some embodiments, the mounting jig 30 includes one or more motors,gears or any other mechanism to change the angle θ′ or θ. Further, themounting jig 30 is also configured to change the position of the entirecleaning device (adhesive sheet) with respect to the photo mask 12.

In some embodiments, the mounting jig 30 is attached or attachable to apod mounting device 40. As shown in FIG. 3, an EUV photo mask is mountedon the inner pod 16 and the inner pod 16 is mounted on the outer pod 15,and the inner pod is dismounted from the outer pod and the photo mask isdismounted form the inner pod. In some embodiments, these mounting anddismounting operations are performed by a pod mounting device 40. Insome embodiments, the mounting and dismounting operations of the photomask on and from the inner pod 16 is performed by a different podmounting device from the pod mounting device for mounting anddismounting operations of the inner pod 16 on and from the outer pod 15.

In some embodiments, after the upper cover 16-4 is removed from theinner pod to expose the back side of the photo mask 12, the cleaningdevice is applied to the chamfered edge of the back side of the photomask 12. When the mounting jig 30 is attached to the pod mounting device40, it is efficient to clean the chamfered edge of the photo mask 12. Insome embodiments, the cleaning is mechanically and automaticallyperformed by using one or more control circuit programmed to control themounting jig 30 and the cleaning device 20 and 20A.

In other embodiments, the mounting jig 30 is attached or attachable toanother independent stage used for the purpose of cleaning.

In some embodiments, as shown in FIG. 12, an adhesive sheet 22B ismanually applied to the chamfered edge of the back side of the photomask 12.

In some embodiments, the cleaning device includes a body 28 and aflexible support having a frame shape and an inclined surface, and anadhesive sheet or tape is attached on the inclined surface (applicatorsurface). The inclined surface has an inclined angle θ, which is about40 degrees to 50 degrees, in some embodiments, and the angle θ is 45degrees in a certain embodiment. In some embodiments, the flexiblesupport has a larger or smaller flexibility than the adhesive sheet. Insome embodiments, the flexible support includes rubber, sponge, polymer,or other suitable material. In some embodiments, the thickness of theadhesive sheet is in a range from about 0.5 mm to about 5 mm, and is ina range from about 1 mm to about 3 mm.

In use, the cleaning device is applied to the backside of photo mask 12from above so that the adhesive sheet contact the chamfered edges of thephoto mask 12. The cleaning device is pressed to the photo mask 12 suchthat the flexible support deforms. By repeating the pressing anddetaching of the cleaning device, the edge of the photo mask 12 iscleaned. In some embodiments, the cleaning device 12 is rotated by 90 or180 degrees after detaching from the photo mask 12. Vibration as setforth above may be applied during the pressing the cleaning device tothe photo mask. In some embodiments, the flexible body is made of thematerials for the adhesive tape and is made of silicone, astyrene-ethylene-butylene-styrene copolymer, astyrene-ethylene-propylene-styrene copolymer, or any other suitableadhesive material. In such a case, the adhesive tape is not necessary.In some embodiments, the cleaning device is applied to the photo mask 12by an automated mechanical structure.

FIGS. 13A and 13B show a process flow of cleaning an EUV photo maskaccording to embodiments of the present disclosure.

In FIG. 13A, after the EUV photo mask is used in an EUV lithographyapparatus, the EUV photo mask is unloaded from the EUV lithographyapparatus. In some embodiments, the EUV photo mask is loaded into aninner pod in a vacuum state. Then, the inner pod is unloaded from thevacuum apparatus and is loaded into an outer pod of the mask pod device.Then, the mask pod device is loaded on a pod dismounting device and theouter pod and inner pod are removed. In some embodiments, the pellicleis removed before the photo mask is loaded into the inner pod. Then, thephoto mask is subjected to a cleaning operation in some embodiments. Insome embodiments, the cleaning operation includes cleaning the entirephoto mask by a wet and/or dry cleaning. In some embodiments, thecleaning operation includes the cleaning the chamfered edges of thebackside of the photo mask as explained above. After the cleaningoperation, the photo mask is loaded into a mask library or a maskstocker.

In FIG. 13B, when an EUV photo mask is used, the photo mask is unloadedfrom the mask library or stocker and then subjected to the cleaningoperation. In some embodiments, the cleaning operation includes cleaningthe entire photo mask by a wet and/or dry cleaning. In some embodiments,the cleaning operation includes cleaning the chamfered edges of thebackside of the photo mask as explained above. After the cleaningoperation, if a pellicle was not mounted over the photo mask, a pellicleis mounted over the photo mask. Then, the photo mask is loaded into aninner pod and the inner pod is loaded into an outer pod, and the maskpod device is transferred to an EUV lithography apparatus. The inner podis removed from the outer pod in a vacuum state, and the inner pod istransferred to the lithography apparatus. In the EUV lithographyapparatus, the photo mask is unloaded from the inner pod under vacuum,and set on a mask stage of the EUV lithography apparatus.

According to embodiments, of the present disclosure, an adhesive sheetor tape can effectively remove particles on chamfered edges of thebackside of an EUV photo mask. Since the adhesive sheet or tape isrelatively low cost, the cleaning cost can be suppressed. Althoughcleaning methods for an EUV photo mask are explained, the cleaningmethod of the present disclosure can apply to cleaning of any type ofphoto mask, e.g., photo masks for deep UV lithography or UV lithography,or a photo mask without chamfered edges.

It will be understood that not all advantages have been necessarilydiscussed herein, no particular advantage is required for allembodiments or examples, and other embodiments or examples may offerdifferent advantages.

According to some embodiments of the present disclosure, in a method ofcleaning a photo mask, the photo mask is placed on a support such that apattered surface faces down, and an adhesive sheet is applied to edgesof a backside surface of the photo mask. In one or more of the foregoingor following embodiments, the edges of the backside surface of the photomask are chamfered edges. In one or more of the foregoing or followingembodiments, the adhesive sheet is made of silicone. In one or more ofthe foregoing or following embodiments, the adhesive sheet is made of astyrene-ethylene-butylene-styrene copolymer or astyrene-ethylene-propylene-styrene copolymer. In one or more of theforegoing or following embodiments, the adhesive sheet is attached to abody. In one or more of the foregoing or following embodiments, the bodyis made of an elastic material. In one or more of the foregoing orfollowing embodiments, the applying the adhesive sheet comprises movingthe body while the adhesive sheet is in contact with the edges. In oneor more of the foregoing or following embodiments, the moving comprisesa linear movement.

In accordance with another aspect of the present disclosure, in a methodof cleaning a photo mask, the photo mask is loaded into an inner pod,the inner pod is loaded into an outer pod, the outer pod is opened, aninner pod is opened such that the photo mask is placed over a bottomcover of the inner pod with a patterned surface facing down, and anadhesive sheet is applied to edges of a backside surface of the photomask, while the photo mask placed over bottom cover of the inner pod. Inone or more of the foregoing or following embodiments, an adhesive sheetis attached to a surface of a body, and a body is coupled to a grip by arod, and in the applying the adhesive sheet, the grip is operated toclean the edges of the backside surface of the photo mask. In one ormore of the foregoing or following embodiments, the body has acylindrical shape and the adhesive sheet wraps around the body. In oneor more of the foregoing or following embodiments, the applying theadhesive sheet comprises rotating the body. In one or more of theforegoing or following embodiments, the body has a curved surface andthe adhesive sheet is attached to the curved surface. In one or more ofthe foregoing or following embodiments, the applying the adhesive sheetcomprises applying vibration to the body. In one or more of theforegoing or following embodiments, the vibration is in an ultrasoundrange. In one or more of the foregoing or following embodiments, edgesof a patterned surface is not cleaned by the adhesive sheet.

In accordance with another aspect of the present disclosure, a cleaningdevice for removing a particle from an edge of a backside of an EUVphoto mask, includes a first body around which an adhesive tape iswound, a second body to which an end of the adhesive tape is attached,and a driving mechanism to rotate the second body. The adhesive tape ismade of one of silicone, a styrene-ethylene-butylene-styrene copolymeror a styrene-ethylene-propylene-styrene copolymer. In one or more of theforegoing or following embodiments, the cleaning device further includesa mounting jig configured to change an angle between a surface of theadhesive tape and the backside of the photo mask. In one or more of theforegoing or following embodiments, the mounting jig is attached to amask pod mounting-dismounting device. In one or more of the foregoing orfollowing embodiments, the driving mechanism is configured to adjust arotational speed of the second body.

The foregoing outlines features of several embodiments or examples sothat those skilled in the art may better understand the aspects of thepresent disclosure. Those skilled in the art should appreciate that theymay readily use the present disclosure as a basis for designing ormodifying other processes and structures for carrying out the samepurposes and/or achieving the same advantages of the embodiments orexamples introduced herein. Those skilled in the art should also realizethat such equivalent constructions do not depart from the spirit andscope of the present disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

What is claimed is:
 1. A method of cleaning a photo mask, comprising:placing the photo mask on a support such that a patterned surface of thephoto mask faces down; and applying an adhesive sheet to edges of abackside surface of the photo mask.
 2. The method of claim 1, whereinthe edges of the backside surface of the photo mask are chamfered edges.3. The method of claim 1, wherein the adhesive sheet is made ofsilicone.
 4. The method of claim 1, wherein the adhesive sheet is madeof a styrene-ethylene-butylene-styrene copolymer or astyrene-ethylene-propylene-styrene copolymer.
 5. The method of claim 1,wherein the adhesive sheet is attached to a body.
 6. The method of claim5, wherein the body is made of an elastic material.
 7. The method ofclaim 5, wherein the applying the adhesive sheet comprises moving thebody while the adhesive sheet is in contact with the edges.
 8. Themethod of claim 7, wherein the moving comprises a linear movement.
 9. Amethod of cleaning a photo mask, comprising: loading the photo mask intoan inner pod; loading the inner pod into an outer pod; opening the outerpod; opening the inner pod such that the photo mask is placed over abottom cover of the inner pod with a patterned surface of the photo maskfacing down; and applying an adhesive sheet to edges of a backsidesurface of the photo mask, while the photo mask is placed over thebottom cover of the inner pod.
 10. The method of claim 9, wherein: theadhesive sheet is attached to a surface of a body, and the body iscoupled to a grip by a rod, and applying the adhesive sheet comprisesoperating the grip to clean the edges of the backside surface of thephoto mask.
 11. The method of claim 10, wherein the body has acylindrical shape and the adhesive sheet wraps around the body.
 12. Themethod of claim 11, wherein the applying the adhesive sheet comprisesrotating the body.
 13. The method of claim 10, wherein the body has acurved surface and the adhesive sheet is attached to the curved surface.14. The method of claim 10, wherein the applying the adhesive sheetcomprises applying vibration to the body.
 15. The method of claim 14,wherein the vibration is in an ultrasound range.
 16. The method of claim9, wherein edges of the patterned surface of the photo mask are notcleaned by the adhesive sheet.
 17. A cleaning device for removing aparticle from an edge of a backside of an EUV photo mask, the cleaningdevice comprising: a first body around which an adhesive tape is wound;a second body to which an end of the adhesive tape is attached; and adriving mechanism to rotate the second body, wherein the adhesive tapeis made of one of silicone, a styrene-ethylene-butylene-styrenecopolymer or a styrene-ethylene-propylene-styrene copolymer.
 18. Thecleaning device of claim 17, further comprising a mounting jigconfigured to change an angle between a surface of the adhesive tape andthe backside of the photo mask.
 19. The cleaning device of claim 18,wherein the mounting jig is attached to a mask pod mounting-dismountingdevice.
 20. The cleaning device of claim 17, wherein the drivingmechanism is configured to adjust a rotational speed of the second body.